Ethylene is a cornerstone of the petrochemical industry. For example, the dimerization of ethylene to 1-butene plays a key role in the production of alkylate gasoline and of linear low-density polyethylene. Overall, ethylene oligomerization is one of the largest industrial transformations enabled by homogeneous catalysts, exceeded in volume only by hydroformylation, hydrocyanation, and methanol carbonylation. The prominence of ethylene dimerization in the overall industrial production of 1-butene is projected to rise further with the increasing reliance on natural gas feedstocks. Despite substantial academic and industrial efforts, the development of heterogeneous catalysts for ethylene dimerization has suffered from either a lack of activity or poor selectivity. Addressing the selectivity challenge is particularly difficult because, for example, small changes in the ligand sphere or electronic structure of the metal can change the relative rates of ethylene insertion versus beta-hydride elimination, which together relate to product distribution. Such degree of fine tuning in ligand design is the realm of homogeneous catalysis and has not traditionally been available to heterogeneous systems.
Accordingly, improved compositions and methods are needed.